Do you have sources of such countries? I know at least one case - russia (before the war) - where they gave out cash and really cheap mortgages and it caused a little baby boom so it worked. I have not heard of any such programs in the developed world…
In France, the policies are measurably motivating having more children according to some studies (can't link them right now). The effect size is on the order of +0.3 to the TFR rate or something like that.
The are many programs like this all over the world; the issue with them is they don't give out enough money/resources to have a measurable positive effect - they should be much much more funded. Incidentally the biggest baby boom in my country (Slovakia) was during the largest buildout of cheap accomodation for young families in the history, also the maternity leave was increased to 3 years and there were various subsidies. So I think policies like that work if they are properly funded.
